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Mercury Return Mission
Back to Mercury Activities A Mercury return mission is very difficult because of the high amount of fuel needed in order to spend all the Delta-v required. In order to complete this mission, players have to build a massive ship or conduct multiple flybys. The Ship A mission to Mercury requires huge amounts of fuel. In addition, the planet lacks an atmosphere, so landing must be done with the engines. The best way to do this mission is to get the paid version which will allow you to build larger ships, to merge ships, and to exchange fuel. Still, the mission is possible with the free version. Some players suggest the use of helping ships. Helping ships can push the main ship out of Earth's atmosphere, push it out of Earth's Sphere of Influence, push a ship out of Mercury's orbit or land on Mercury, to help send the main ship into orbit. In addition, if you use the paid version, helping ships can refill the fuel tanks. The game has no pre-built ships and any player is free to build its own spacecraft. The ship listed on top-right of this article I named it Ana Express or simply AX (feel free to name it as you want in your game). It is a three-stage rocket with two boosters on the third stage. It is ideal for return missions to Mercury, Mars and Venus. The first stage is made of seven big engines, with 140 t of fuel. The second stage has two big engines available to use with the first stage, together with 35 t of fuel. The other 5 engines, with their 100 t of fuel are used only after the first stage is detached. The third stage has two detachable boosters, with a total of four small engines and 20 t of fuel. They also have two landing legs and two side parachutes. Because Mercury has no atmosphere, the parachutes are useless and should be removed to reduce mass. The landing legs are vital for the mission. The central rocket of the second stage has a small engine, 10 t of fuel, a Capsule, and a parachute. Liftoff The mission allows for some error, but not too much. At launch, all seven engines of the first stage and the two separate engines of the second stage must be turned on, working at 100%. At 4000-5000 meters, where the atmosphere is denser, the ship must fly vertically, to pass faster. After this, the ship must gradually turn aside. Above 10 km, Earth's atmosphere is rarefied and will not cause significant problems. The first stage needs to be separated when it runs out of fuel, then it will fall back to Earth. Earth Orbit The second stage will carry the used two engines and their fuel tanks. Because of the limited building space, there is no other way. While using the second stage, the ship has to change angle to gain low Earth orbit. In order to save as much fuel as possible, this must be done smoothly. Flight path must not get too far from the Karman Line. After gaining orbit, some correction maneuvers must be done to get an orbit as circular as possible. If everything is done perfectly, the second stage must still have little fuel left. If low Earth orbit cannot be gained with the second stage, it is best to abort the mission. Cruise To Mercury There are 3 different ways to get to Mercury: directly, with the help of flybys, or with the help of Venus aerobraking. Direct Cruise This is the fastest and easiest way. However, fuel consumption will be huge. The ship will fly by Mercury very fast, so that it will need a lot of fuel to slow down and gain orbit. This technique can be performed well if you have a huge ship, as allowed by the paid version. With the free version of the game, the ship might not have enough fuel to return after a landing. Mercury has a very small sphere of influence. To gain the correct trajectory, you need to do some very precise engine burns. Flybys The most commonly used method to reach Mercury is to use at least one Venus flyby meaning a mission to Mercury starts like a mission to Venus. This will lower the perihelion below the orbit of Venus and the aphelion below the orbit of Earth. It might be necessary to conduct two Venus flybys. A more complex way to reach Mercury is the use of many flybys. A ship can escape Earth's sphere of influence with the help of two Moon flybys. Then, with the use of up to five Earth flybys, it can lower perihelion to Venus orbit. Finally, two Venus flybys are enough to reach Mercury's orbit. However, even with all this, the ship might not be slowed enough. Entering orbit around Mercury might still require a lot of fuel. One or two Mercury flybys should be enough to solve this problem. The use of multiple flybys is difficult. The ship might spend more fuel on multiple flybys then is would spend on a direct Earth - Mercury flight. Aerobrake This technology is efficient, but risky. The ship must first fly towards Venus, then slightly pass through the outer layer of the atmosphere. This will slow the ship down enough to gain Venus orbit. This method is risky because you can slow too much and land on Venus. From the orbit of Venus, a ship can use a flight window to reach Mercury. With the help of one or two Mercury flybys, landing should be possible. Mercury Orbit When a ship enters Mercury's sphere of influence, it usually has great speed. Slowing down requires significant fuel. This is why it is important to decrease speed by using at least one Mercury flyby. If the ship has a velocity below 500 m/s when entering Mercury's sphere of influence, it can slow down without problems. It is good to make the ship first gain a low Mercury orbit before landing. Mercury Landing In order to land, the ship needs to turn on the engines. The best way to land is from a low orbit. First, the engines must burn retrograde while the ship orbits around the planet. Then, as the ship descends on a vertical trajectory, the engines must slow it down for a soft landing. For the AX ship, fuel consumption should be like this: At the first Venus flyby, boosters should be 1/3 empty. When Mercury orbit is achieved, boosters should be 2/3 empty. Finally, at Mercury touchdown, there should be no or nearly no more fuel in the boosters. In this case, the ship will land together with its boosters and separate them on the surface. As an alternative (mainly if there still is some fuel left in the boosters), detach them after liftoff. If they are detached on the ground, there is a small risk that they will push the ship over. Back To Orbit From Mercury's surface, liftoff is easy. Without an atmosphere, it is easy to achieve orbit. First, fly up, then turn to one side. Mercury has a low gravity, comparable with Mars. To get a circular low Mercury orbit, a few trajectory correction maneuvers are required. Cruise Back Just like the cruise to Mercury, there are 3 ways to get back to Earth: a direct route, with the use of multiple flybys or first with a stop around Venus, with the help of aerobraking. Each player should consider its choices. The AX ship has a central rocket on the third stage which might be enough for a direct flight towards Earth if it has no used fuel. Earth Landing Earth has a dense atmosphere, but not dense enough for a direct impact. Try to hit the atmosphere at an angle. Set the flight path so that the ship should touch the surface but not fly towards the core of Earth. The ship should reach Earth with very little fuel left. The atmosphere will slow down the ship just enough to open the parachute. Important: If the flight path is set towards Earth's center, the atmosphere might not slow the ship enough. Sometimes, the impact with Earth's surface might cause the destruction of one engine. When landing on mountains, the ship might suffer from an impact and turn over, destroying the capsule. To avoid dangers, it is good to still have some fuel left for a small engine burn two seconds before touchdown. See Also *Mercury *Mercury Activities *What To Do In Spaceflight Simulator Category:Tutorial